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Gold nanospheres that bake tumours to death by attracting the heat of low-powered lasers have been developed by scientists in California.

"You could send a person home, have them shine a laser on the specific part of the body with cancer for a couple weeks, and they could be cured of cancer," says Professor Jin Zhang of the University of California in Santa Cruz who helped develop the nanoparticles.

To create the gold nanospheres, the scientists started with nanospheres made from cobalt, then replaced the cobalt atoms with gold atoms, using the same process that turns the calcium in dinosaur bones into fossils.

The gold nanospheres are then coated in antibodies that detect, and then latch onto, cancer cells.

Once the nanospheres attach to cancer cells their uniform size of 30 nanometres becomes important in destroying the cancer cells.

Gold nanospheres of that size respond to a narrow range of infrared light by becoming hot. When the laser is shined onto the skin, the nanospheres heat up to searing temperatures and essentially bake the cancer cells to death.

If the gold nanospheres had different sizes, they would respond to different wavelengths of light.

To compensate, scientists would have to either add a step to sort the nanospheres by size or inject more of them into the blood stream.

Fast acting

To test their idea, scientists intravenously injected skin cancer-ridden mice with a solution of the gold nanoparticles.

After four hours the gold nanospheres had used their antibody-antigen to latch onto the harmful cells. Scientists shined a laser beam onto the mice, killing the cancer cells.

Once the nanoparticles have done their job and destroyed the tumour, the kidneys filter them out of a patient's body within a few hours, says Professor Shouheng Sun, of Brown University who also studies gold nanoparticles coated with tumour-specific antibodies.

Gold nanoparticles can be seen on an MRI machine and therefore used to locate a tumour. Sun's team added iron nanoparticles to their gold units since iron nanoparticles can also carry a chemotherapy drug to the tumour.

The antibody-antigen approach to identifying tumour cells is the most important part of all the research, Sun says.

"Right now the biggest problem is that there is no capability to identify cancer cells," he says.

"With this new particle we can specifically target the agent for tumour cells, to enhance its therapeutic effects," while minimising the painful side effects of current chemotherapy for cancer patients.